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<h1 style="direction:ltr;"><b><font color="#808000">Functionality</b></font></h1>
<ul><li style="direction:ltr;"><h2>Reliability</h2></li>
<ul><li style="direction:ltr;">Packet-based sequencing</li>
<li style="direction:ltr;">Acknowledgment and loss report from receiver</li>
<li style="direction:ltr;">ACK sub-sequencing</li>
<li style="direction:ltr;">Retransmission (based on loss report and timeout)</li>
</ul><li style="direction:ltr;"><h2>Streaming and Messaging</h2></li>
<ul><li style="direction:ltr;">Buffer/memory management</li>
</ul><li style="direction:ltr;"><h2>Connection maintenance</h2></li>
<ul><li style="direction:ltr;">Handshake, keep-alive message, teardown message</li>
</ul><li style="direction:ltr;"><h2>Duplex</h2></li>
<ul><li style="direction:ltr;">Each UDT instance contains both a sender and a receiver</li>
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<h3>Notes:</h3>
<p style="direction:ltr;"><font color="#000000">Let's review the functionalities first.</font></p>
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<p style="direction:ltr;"><font color="#000000">The reliability control is provided by sequencing and acknowledgment. Each UDT packet is assigned a unique increasing sequence number. The receiver will send back acknowledgments and loss reports according to packet arrival. Lost packets will be retransmitted.</font></p>
<p style="direction:ltr;"><font color="#000000"></font></p>
<p style="direction:ltr;"><font color="#000000">The streaming service is implemented in buffer management.</font></p>
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<p style="direction:ltr;"><font color="#000000">UDT also has a series of mechanisms to set up, maintain, and tear down a UDT connection.</font></p>
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<p style="direction:ltr;"><font color="#000000">Finally, each UDT instance has both a sender and receiver, in order to provide duplex data transfer service.</font></p>
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